Image processing apparatus and method

ABSTRACT

When one viewing condition parameter is applied to all pixels, a visual effect between a single color and a background expressed on a rasterized image cannot be reflected on a color matching result. To prevent this, when color matching using a human color appearance model is to be performed, the distance between an image and a viewer and the resolution of the image are input. On the basis of the input distance and resolution, a stimulus region, adjacent region, and background region based on a plurality of field angles (e.g., 2°, 4°, and 10°) for a pixel of interest on the image are defined, thereby determining a viewing condition parameter and performing color matching.

FIELD OF THE INVENTION

[0001] The present invention relates to an image processing apparatusand method and, more particularly, to color matching under differentviewing conditions.

BACKGROUND OF THE INVENTION

[0002] A human color appearance model is so designed as to allowcorrectly predicting how a color is seen when a color chip having afield angle of 2° is given. FIG. 1 is a view showing the definition of ahuman visual field. A CIE 1931 standard calorimetric observer isapplicable to the range of a field angle of 1° to 4°. Therefore, thisapplicable region is divided into a stimulus region having a field angleof 2° or less, an adjacent region having a field angle of 4° or less, abackground region from the adjacent region to a region having a fieldangle of 10°, and a surrounding region around this background region.Also, a visual field region including all these regions is an adaptationregion.

[0003] CIE CAM97s is a representative color appearance model, and inthis model the following can be set as viewing condition parameters.

[0004] La: Absolute luminance [cd/m²] in adaptation region

[0005] Normally, 20% of white point absolute luminance in adaptationregion

[0006] XYZ: Relative XYZ value of color chip

[0007] XwYwZw: Relative XYZ value of white point

[0008] Yb: Relative luminance of background region

[0009] Surround conditions:

[0010] Average Surround (larger than a field angle of 4° of a colorchip)

[0011] Average Surround (equal to or smaller than a field angle of 4° ofa color chip)

[0012] Dim Surround

[0013] Dark Surround

[0014] Cut-Sheet Transparencies (on viewing box)

[0015] The surround condition is Average if the relative luminance inthe surrounding region is 20% or less of a white point in the adaptationregion, Dim if this value is smaller than 20%, and Dark if this value isalmost 0%.

[0016] A color appearance model is derived from experimental resultsusing monochromatic color chips. Hence, no method has been establishedwhich determines viewing condition parameters applicable to an imagehaving a plurality of colors. That is, the relative luminance Yb of thebackground region is set at 20% because neutral gray is 20% of a whitepoint.

[0017] Also, when a color appearance model is applied to an image, oneviewing condition parameter is generally used for all pixels.

[0018] When one viewing condition parameter is thus applied to allpixels, a visual effect between a single color and a backgroundexpressed on a rasterized image cannot be reflected on a color matchingresult.

[0019] Furthermore, since an average viewing condition parameter isevenly applied to an image, no color matching result having highaccuracy can be locally obtained.

SUMMARY OF THE INVENTION

[0020] The present invention has been made to individually orsimultaneously solve the above problems, and has as its object toreflect a visual effect between a single color and a backgroundexpressed on an image onto a color matching result.

[0021] It is another object of the present invention to locally obtain ahigh-accuracy color matching result.

[0022] To achieve the above objects, a preferred embodiment of thepresent invention discloses an image processing apparatus for performingcolor matching by using a color appearance model, comprising aninputter, arranged to input a distance between an image and a viewer,and a resolution of the image, and a processor, arranged to defineregions based on a plurality of field angles with respect to a pixel ofinterest on the image, on the basis of the input distance andresolution, thereby performing color matching.

[0023] Also, an image processing method of performing color matching byusing a color appearance model, comprising the steps of inputting adistance between an image and a viewer, and a resolution of the image,and defining regions based on a plurality of field angles with respectto a pixel of interest on the image, on the basis of the input distanceand resolution, thereby performing color matching is disclosed.

[0024] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a conceptual view showing the definition of a humanvisual field;

[0026]FIG. 2 is a view for explaining the concept of color matching byCAM;

[0027]FIG. 3 is a flow chart showing the process configuration of thefirst embodiment;

[0028]FIG. 4 is a view for explaining the distance from a monitor screenor a printed product to a viewer;

[0029]FIG. 5 is a view for explaining a method of calculating thediameters of a stimulus region, adjacent region, and background regionfrom a distance D between an image and a viewer;

[0030]FIG. 6 is a view showing a pixel of interest in an image andregions corresponding to different field angles;

[0031]FIG. 7 is a view showing lack of pixels in processing near theedge of an image;

[0032]FIG. 8 is a flow chart showing the process configuration of thesecond embodiment;

[0033]FIG. 9 is a view showing an arrangement in which a distancemeasurement sensor is placed on a monitor or a viewing box; and

[0034]FIG. 10 is a view showing a user interface for setting relativeluminance values for lacking pixels in processing near the edge of animage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Image processing apparatuses according to embodiments of thepresent invention will be described in detail below with reference tothe accompanying drawings.

[0036] First Embodiment

[0037] [Concept of Color Matching]

[0038]FIG. 2 is a view for explaining the concept of color matching.

[0039] In FIG. 2, reference numeral 11 denotes a conversion matrix orconversion lookup table (LUT) for transforming data depending on aninput device into device-independent color space data which is based onthe white point reference of environmental light at the input side; 12,a color appearance model transform unit (CAM) for transforming the dataobtained from the conversion LUT 11 into a human color appearance spaceJCh or QMh; 13, JCh (or JCH) which is a color appearance space relativeto the reference white point of environmental light; 14, QMh (or QMH)which is an absolute color appearance space which changes its size inaccordance with an illuminance level; 15, a color appearance modelinverse transform unit (CAM⁻¹) for transforming the human colorappearance space JCh or QMh into device-independent color space databased on the reference white point of environmental light at the outputside; 16, a conversion LUT for transforming the data obtain from theinverse transform unit 15 into color space data depending on an outputdevice; 17, a viewing condition parameter on the input side; and 18, aviewing condition parameter on the output side.

[0040] Note that the input and output devices are not limited to colorspaces such as RGB and CMY(K), but can be arbitrary image input/outputdevices such as a digital still camera, digital video camera, monitor,and printer. Note also that a computer apparatus such as a personalcomputer is applicable to an image processing apparatus for executingcolor matching itself, but this function can also be imparted to theinput/output devices.

[0041] Generally, a white point of environmental light under viewingconditions is different from a white point of a standard light sourcewhen a color chip such as a color target or color patch is measured. Forexample, a standard light source used in colorimetry is D50 or D65.However, environmental light when an image is actually viewed is notrestricted to D50 or D65 but is often illuminating light such as anincandescent lamp or fluorescent lamp or mixed light of illuminatinglight and sun light. In the following explanation, the light sourcecharacteristics of environmental light under viewing conditions are D50,D65, or D93 for the sake of simplicity. In practice, however, the XYZvalue of a white point on a medium is set as a white point.

[0042] When CIE CAM97s, for example, is applied as a color appearancemodel, the viewing condition parameter 17 on the input side and theviewing condition parameter 18 on the output side are as follows.

[0043] La: Absolute luminance [cd/m²] in adaptation region

[0044] XYZ: Relative XYZ value of color chip

[0045] XwYwZw: Relative XYZ value of white point

[0046] Yb: Relative luminance of background region

[0047] Surround conditions:

[0048] Average Surround (average, larger than a field angle of 4° of acolor chip)

[0049] Average Surround (average, equal to or smaller than a field angleof 4° of a color chip)

[0050] Dim Surround (dim)

[0051] Dark Surround (dark)

[0052] Cut-Sheet Transparencies (on viewing box)

[0053] Input device-dependent image data is transformed into a relativeXYZ value under environmental light at the input side by thetransformation LUT 11.

[0054] [Process Configuration]

[0055]FIG. 3 is a flow chart showing the process configuration of thisembodiment. Although a practical hardware arrangement for implementingthe process configuration will not be explained, this processconfiguration is implemented by supplying a program corresponding to theconfiguration to a personal computer or the like.

[0056] First, a user inputs a distance D between an image and a viewer(S21). As shown in FIG. 4, the distance between a monitor screen or aprinted product to a viewer is 0.4 to 0.7 m. However, a given distance Dcan be set by user input. In this embodiment, D=0.5 m is used as anexample. Note that the set value of the distance D between an image anda viewer on the input side can be different from that on the outputside.

[0057] Next, the diameters of a stimulus region, adjacent region, andbackground region are calculated from the distance D between an imageand a viewer. As FIG. 5 shows, the line of sight and the surface of animage presumably intersect at a substantially right angle. Therefore, adiameter Da of the stimulus region having a field angle of 2° or less, adiameter Dp of the adjacent region having a field angle of 4° or less,and a diameter Db of the background region having a field angle of 10°or less are as follows.

Da=2×D×tan(1°)

Dp=2×D×tan(2°)

Db=2×D×tan(5°)

[0058] If D=0.5 m, Da=17 mm, Dp=35 mm, and Db=87 mm.

[0059] The user inputs resolution R (pixels/inch) of an image (S23). Forexample, this resolution R is 72 ppi for an image displayed on a monitorand 400 ppi, which is a printer resolution, for a printout image. Inpractice, the resolution R depends upon a resolution or a zoom ratiodesignated by an application or a device driver. Note that thisresolution has the same value at the input and output sides.

[0060] Subsequently, the numbers of pixels on the image corresponding tothe stimulus pixel region, adjacent pixel region, and background pixelregion are calculated (S24). The numbers Dap, Dpp, and Dbp of pixels inthe diameters of the stimulus region, adjacent region, and backgroundregion, respectively, are as follows.

Dap=Da×R/0.0254

Dpp=Dp×R/0.0254

Dbp=Db×R/0.0254

[0061] If D=0.5 m and R=72 ppi, Dap=48.2, Dpp=99.0, and Dbp=246.6. Forsimplicity, as shown in FIG. 6, assume a square region having 2n+1pixels (n is a positive integer) on each side. Length L of one side ofthis square region is calculated such that the area of a circular regionand the area of the square region are equal. Since L={squareroot}{square root over (π)}×D/2=0.886×D, the side lengths of theindividual regions are Lap=43 pixels, Lpp=87 pixels, and Lbp=219 pixels.If D on the input side and D on the output side are different, it isonly necessary to calculate the number of pixels corresponding to thelength of one side of each region independently for the input and outputsides.

[0062] The user then inputs white point absolute luminance Law [cd/m²]of the adaptation region and absolute luminance Ls [cd/m²] of thesurrounding region on the basis of values indicated by a meter and thelike (S25).

[0063] The white point absolute luminance of the adaptation region canbe calculated by the absolute luminance [cd/m²] of a monitor white pointin the case of a monitor, and by (illuminance [lux]/π on a printedproduct) in the case of a printed product. The absolute luminance of thesurrounding region is strictly the absolute luminance of a region havinga field angle larger than 10° with respect to a pixel of interest. Forthe sake of simplicity, however, this absolute luminance is in the caseof a monitor the ambient absolute luminance of the monitor, and in thecase of a printed product the ambient absolute luminance of the printedproduct. Note that different values can be set as each absoluteluminance in accordance with the viewing conditions on the input andoutput sides.

[0064] Subsequently, the surround conditions are determined by, e.g.,the following conditions (S26).

[0065] If 0.2≦Ls/Law, Average Surround

[0066] If 0.06<Ls/Law<0.2, Dim Surround

[0067] If Ls/Law≦0.06, Dark Surround

[0068] If Ls and Law on the input side are different from those on theoutput side, the surround conditions are independently determined on theinput and output sides.

[0069] Next, a pixel of interest with respect to an input image is set(S27). For example, the following processing is performed for all pixelsfrom the upper left to the lower right of the image.

[0070] First, whether the surround condition on the input or output sideis Average Surround is checked (S28). If the condition is AverageSurround, uniformity Sp in the adjacent region is calculated (S29).

[0071] That is, in the adjacent region (including the pixel of interestand the stimulus region) having the side length Lpp, maximum and minimumY values Ymax and Ymin are calculated from the XYZ value of each pixel.Uniformity Sp=(Ymax−Ymin)/100 is then calculated. If, for example,Sp≦0.01, this adjacent region is regarded as a uniform region. If theadjacent region is considered to be a uniform region, Average Surround(larger than a field angle of 4° of a color chip) is applied as thesurround condition; if the adjacent region is nonuniform, AverageSurround (equal to or smaller than a field angle of 4° of a color chip)is applied as the surround condition. Note that if the distance D at theinput side is different from the distance D at the output side, theranges of the adjacent region are also different, so the calculationsare independently performed on the input and output sides.

[0072] Subsequently, in the background region (not including the pixelof interest, stimulus region, and adjacent region) having the sidelength Lbp as shown in FIG. 5, average relative luminance Yb of Y iscalculated from the XYZ value of each pixel (S30). If the distance D atthe input side is different from the distance D at the output side, theranges of the adjacent region are also different, so the calculation isindependently performed on the input and output sides.

[0073] Next, viewing condition parameters on the input and output sidesare set (S31). For example, if the input side is an sRGB monitor (D65,Law=80 [cd/m²], Ls=4.074 [cd/m²]), the output side is a typical officeenvironment (D50, Law=238.7 [cd/m²], Ls=47.74 [cd/m²]), the distance Dbetween an image and a viewer is 0.5 m on both the input and outputsides, and the resolution is 72 ppi, the viewing condition parametersare as follows.

[0074] Input-side viewing condition parameters:

[0075] La=Law×0.2=80×0.2=16 [cd/m²]

[0076] XwYwZw=D65

[0077] Yb=average Y of input-side background region (one side=219pixels) with respect to each pixel of interest

[0078] Surround condition: Dark Surround (Ls/Law=4.074/80=0.051)

[0079] Output-side viewing condition parameters:

[0080] La=Law=0.2=238.7×0.2=47.74 [cd/m²]

[0081] XwYwZw=D50

[0082] Yb=average Y of output-side background region (one side=219pixels) with respect to each pixel of interest

[0083] Surround condition: Average Surround (Ls/Law=47.74/238.7=0.2)

[0084] The average relative luminance Yb on the output side should becalculated from the XYZ value at the output side. However, the XYZ valueon the output side is unpresumable in this stage, so the averagerelative luminance Yb at the output side is approximated by using theXYZ value on the input side. Also, the surround condition on the outputside is Average Surround. Therefore, processing similar to step S29 isperformed; the viewing condition parameter “larger than a field angle of4° of a color chip” or “equal to or smaller than a field angle of 4° ofa color chip” is set in accordance with the uniformity of a partialimage in the adjacent region.

[0085] Finally, color matching is performed by the CAM 12 by using theviewing condition parameters at the input and output sides (S32),thereby calculating the output-side XYZ value corresponding to theinput-side XYZ value. Steps S27 to S32 are repeated until it isdetermined in step S33 that analogous processing is completely performedfor all pixels in the image. In this way, color matching is performedfor the whole image.

[0086] [Processing of Edge of Image]

[0087] If a pixel of interest is set near the edge of an image as shownin FIG. 7, pixels in the stimulus region and the adjacent region areomitted in the process of step S29. Likewise, pixels in the backgroundregion are omitted in step S30. In a case like this, Ymax, Ymin, and Ybare obtained from effective pixels without processing these omittedpixels.

[0088] As another method of preventing a lowering of the processingspeed caused by determination of the presence/absence of omission ofpixels near the edge of an image, a value such as Y=100, Y=20, or therelative luminance of the surrounding region can be set for an omittedpixel (as an omitted pixel) in accordance with the frame or the ambientsituation of an assumed image. In this manner, processing can beperformed without any omitted pixels.

[0089] As described above, the first embodiment can achieve thefollowing effects.

[0090] (1) By using the distance D between an image and a viewer and theresolution R of the image, regions having different field angles (e.g.,2°, 4°, and 10°) with respect to a pixel of interest can be defined onthe image.

[0091] (2) A circular region with respect to a field angle isapproximated to a square region in an image. This can increase the speedof processing in that region.

[0092] (3) By calculating the uniformity Sp at a field angle of 4° orless in an image, it is possible to determine which of “larger than afield angle of 4° of a color chip” or “equal to or smaller than a fieldangle of 4° of a color chip” is to be used as a viewing conditionparameter of Average Surround.

[0093] (4) By calculating the average relative luminance Yb of thebackground region with respect to a pixel of interest in an image, thisvalue can be set as a viewing condition parameter for the pixel ofinterest.

[0094] (5) In processing near the edge of an image, a specific value(e.g., Y=100, Y=20, or the relative luminance of the surrounding region)is set for omitted pixels in the adjacent region and the backgroundregion. This can increase the speed of the processing near the edge.

[0095] Second Embodiment

[0096] An image processing apparatus of the second embodiment accordingto the present invention will be described below. In the secondembodiment, the same reference numerals as in the first embodimentdenote the same parts, and a detailed description thereof will beomitted.

[0097] In the first embodiment, an image object or a rasterized objecthas been primarily explained. In the second embodiment, color matchingmentioned above is applied to a graphical object before rasterization.

[0098] Average relative luminance Yb of the background region can beobtained by analyzing the order of overlap of objects, and referring tocolors in the objects and the colors of objects in the background inaccordance with the sizes of the objects. A method of determiningwhether “larger than a field angle of 4° of a color chip” in the case ofAverage Surround will be explained as an example.

[0099]FIG. 8 is a flow chart showing the process configuration of thesecond embodiment.

[0100] First, a vector image to be displayed on a monitor or printed outis input (S71), and the type of the input object is detected (S72 toS75). If the input object is not detected as any object, the process isterminated by displaying an error message (S76).

[0101] If input object is text object or closed loop object

[0102] In this case, processes corresponding to steps S21 to S26 shownin FIG. 3 are performed in initialization (S77) to predetermine a region(adjacent region) corresponding to a field angle of 4° and a surroundcondition.

[0103] Subsequently, whether the surround condition is Average Surroundis checked (S78). If the condition is Average Surround, a rectanglecontaining the object is calculated for simplification, and whether thisrectangle is larger than the region having a field angle of 4° ischecked. That is, a rectangle containing the object is extracted (S79).This rectangle containing the object is compared with a square(equivalent to Lpp=87 pixels if D=0.5 m and R=72 ppi) having a fieldangle of 4°, thereby optimizing a viewing condition parameter for theobject (S80).

[0104] More specifically, in the process of step S80, if bothlongitudinal and lateral sides of the rectangle are larger than Lpp, itis determined that “larger than a field angle of 4°”. If one of thelongitudinal and lateral sides is shorter, the analysis is furtheradvanced. If the short side of the rectangle ≧0.8×Lpp and the area islarger than the region (Lpp [m²]) having a field angle of 4°, it isdetermined that “larger than a field angle of 4°”; if not, it isdetermined that “equal to or smaller than a field angle of 4°”. Notethat this determination is applicable only when the text or the closedloop is painted with a single color. To increase the accuracy of thedetermination, it is also possible to calculate the area (occupiedratio) of a region actually painted in the rectangular region containingthe object.

[0105] If input object is image object

[0106] In this case, a viewing condition parameter is optimized byprocesses equivalent to steps S21 to S31 shown in FIG. 3 (S81).

[0107] If input object is line object

[0108] When this is the case, the possibility of “larger than a fieldangle of 4° of a color chip” is low. Therefore, the process ofoptimizing a viewing condition parameter is skipped.

[0109] When a viewing condition parameter for each object is set by theabove processing, color matching by a CAM 12 is performed (S82). Theprocesses from steps S72 to S82 are repeated until it is determined instep S83 that all objects are completely processed. In this way, colormatching of the whole vector image is completed.

[0110] By thus detecting objects, processing for a field angle can beperformed not only for a raster image but also for a vector image.

[0111] Third Embodiment

[0112] An image processing apparatus of the third embodiment accordingto the present invention will be described below. In the thirdembodiment, the same reference numerals as in the first embodimentdenote the same parts, and a detailed description thereof will beomitted.

[0113] In step S21 of FIG. 3, a user inputs a distance D between animage and a viewer. This process can be automated by the use of adistance measurement sensor. As an example, a distance measurementsensor which measures a distance on the basis of the reflection time ofinfrared radiation is placed on a monitor or a viewing box (FIG. 9).

[0114] If a measurement sensor is difficult to install or is notconnected to a host, the distance D can be manually set. It is of coursealso possible to input a numerical value (distance) displayed on ameasurement sensor when the sensor is offline (not connected to a hostmachine).

[0115] Furthermore, in processing near the edge of an image, a relativeluminance value for an omitted pixel can be set by a user interfaceshown in FIG. 10. Although a default value is 20%, 100% can be set whenthe background is white, and an ambient relative luminance value can beset for a frameless image. If an actual relative luminance value isobtained, a custom value can also be input.

[0116] As described above, the distance D between a user and anoriginal, monitor, or printed product can be accurately set by the useof a distance measurement sensor.

[0117] Modification of the Embodiments

[0118] In each of the above embodiments, the magnification of an imageis not changed. However, a viewing condition parameter can also be setin accordance with zoom magnification Z. For example, if the sides ofthe stimulus region, adjacent region, and background region with respectto a direct image are Lap, Lpp, and Lbp, respectively, when the distanceD between an image and a viewer and the resolution R of the image aregiven, the sides of these regions with respect to the zoom magnificationZ are given as follows on the original image if the distance D is fixed.By using these values in the aforementioned processing, the processingcan be controlled even when the magnification of the image is changed.

Lap′=Lap×(1/Z)

Lpp′=Lpp×(1/Z)

Lbp′=Lbp×(1/Z)

[0119] The present invention can be applied to a system constituted by aplurality of devices (e.g., host computer, interface, reader, printer)or to an apparatus comprising a single device (e.g., copy machine,facsimile).

[0120] Further, the object of the present invention can be also achievedby providing a storage medium storing program codes for performing theaforesaid processes to a system or an apparatus, reading the programcodes with a computer (e.g., CPU, MPU) of the system or apparatus fromthe storage medium, then executing the program.

[0121] In this case, the program codes read from the storage mediumrealize the functions according to the embodiments, and the storagemedium storing the program codes constitutes the invention.

[0122] Further, the storage medium, such as a floppy disk, a hard disk,an optical disk, a magneto-optical disk, CD-ROM, CD-R, a magnetic tape,a non-volatile type memory card, and ROM can be used for providing theprogram codes.

[0123] Furthermore, besides aforesaid functions according to the aboveembodiments are realized by executing the program codes which are readby a computer, the present invention includes a case where an OS(operating system) or the like working on the computer performs a partor entire processes in accordance with designations of the program codesand realizes functions according to the above embodiments.

[0124] Furthermore, the present invention also includes a case where,after the program codes read from the storage medium are written in afunction expansion card which is inserted into the computer or in amemory provided in a function expansion unit which is connected to thecomputer, CPU or the like contained in the function expansion card orunit performs a part or entire process in accordance with designationsof the program codes and realizes functions of the above embodiments.

[0125] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the claims.

What is claimed is:
 1. An image processing apparatus for performingcolor matching by using a color appearance model, comprising: aninputter, arranged to input a distance between an image and a viewer,and a resolution of the image; and a processor, arranged to defineregions based on a plurality of field angles with respect to a pixel ofinterest on the image, on the basis of the input distance andresolution, thereby performing color matching.
 2. An image processingmethod of performing color matching by using a color appearance model,comprising the steps of: inputting a distance between an image and aviewer, and a resolution of the image; and defining regions based on aplurality of field angles with respect to a pixel of interest on theimage, on the basis of the input distance and resolution, therebyperforming color matching.
 3. The method according to claim 2, whereinat least 2°, 4°, and 10° are used as the plurality of field angles. 4.The method according to claim 2, wherein in the color matching step,circular regions corresponding to the plurality of field angles areapproximated to square regions to thereby increase the speed ofprocessing in the regions.
 5. The method according to claim 2, whereinin the color matching step, a viewing condition parameter for the pixelof interest is determined by using pixel values of regions correspondingto the plurality of field angles.
 6. The method according to claim 2,wherein in the color matching step, on the basis of the uniformity ofthe image within the field angle of a color chip in the color appearancemodel, a parameter selected from the group consisting of “larger thanthe field angle of the color chip” and “not more than the field angle ofthe color chip” is used as an average surrounding viewing conditionparameter.
 7. The method according to claim 2, wherein in the colormatching step, the average relative luminance of a background regionwith respect to the pixel of interest is used as a viewing conditionparameter for the pixel of interest.
 8. The method according to claim 2,wherein in the color matching step, a speed of processing performed nearan edge of the image is increased by setting a specific value foromitted pixels in an adjacent region and a background region.
 9. Themethod according to claim 8, wherein the specific value is selected fromthe group consisting of a luminance of 100%, a luminance of 20%, and therelative luminance of a surrounding region.
 10. The method according toclaim 2, wherein in the color matching step, a viewing conditionparameter for each object on a vector image is determined by using theranges of regions corresponding to the plurality of field angles. 11.The method according to claim 2, further comprising the step ofmeasuring the distance between the image and the viewer.
 12. The methodaccording to claim 2, further comprising the step of manually inputtingthe distance between the image and the viewer.
 13. The method accordingto claim 2, further comprising the step of manually inputting therelative luminance of a portion selected from the group consisting ofthe edge and the frame of the image.
 14. A computer program productcomprising a computer readable medium storing a computer program code,for an image processing method of performing color matching by using acolor appearance model, comprising a process procedure code for:inputting a distance between an image and a viewer, and a resolution ofthe image; and defining regions based on a plurality of field angleswith respect to a pixel of interest on the image, on the basis of theinput distance and resolution, thereby performing color matching.
 15. Animage processing method of performing color matching by using a colorappearance model, comprising the steps of: inputting a distance betweenan image and a viewer, and a resolution of the image; obtaining abackground image for a pixel of interest on the image on the basis ofthe input distance and resolution; obtaining an average relativeluminance value for the pixel of interest from pixel values in theobtained background region; and performing color matching using thecolor appearance model for the pixel of interest, by using the obtainedaverage relative luminance value.
 16. A computer program productcomprising a computer readable medium storing a computer program code,for an image processing method of performing color matching by using acolor appearance model, comprising a process procedure code for:inputting a distance between an image and a viewer, and a resolution ofthe image; obtaining a background image for a pixel of interest on theimage on the basis of the input distance and resolution; obtaining anaverage relative luminance value for the pixel of interest from pixelvalues in the obtained background region; and performing color matchingusing the color appearance model for the pixel of interest, by using theobtained average relative luminance value.